This paper discusses how to optimize the weighting of individual subarrays to derive the low sidelobe level (SLL) based on quadratic programming (QP) and how to derive QP parameters to ensure that the objective function is composed of the quadratic function form, with the actual number identical to the standard objective function of QP. Next, in order to analyze the SLL, a 24 × 24 phased array antenna was compared with 96 transmit–receive modules (TRMs) attached only to the subarray stage and a phased array antenna with 576 TRMs attached to all radiating elements without a subarray. Optimized weighting was applied to the array antennas with a subarray, and Taylor weighting was applied to the array antennas without a subarray. The number of TRMs used in the phased array antenna with the optimized weighting was reduced by 83.3% compared to the phased array antenna in which TRMs were attached to all radiating elements. The SLL and the half-power beamwidths (HPBWs) of the two antennas were practically identical in a narrow beam-scanning environment. Finally, an array pattern (AP) in which mutual coupling between the radiating elements was considered was calculated to verify the optimized weighting. Moreover, the optimized weighting was applied to CST Microwave Studio (an EM full-wave simulation) to compare the results from the AP calculation and a simulation. It was confirmed that the two results above are largely indistinguishable. The analysis found that the HPBW is 3.6${}^{\circ }$ × 3.6${}^{\circ }$ and the SLL is −26.18 dB from AP calculations in the boresight direction. When each 5${}^{\circ }$ beam was scanned at the azimuth and elevation, the corresponding HPBW values were 3.7${}^{\circ }$ × 3.7${}^{\circ }$ and 3.7${}^{\circ }$ × 3.7${}^{\circ }$ and the SLLs were −22.70 dB and −24.44 dB according to the AP calculations.

In this paper, a hybrid waveguide feed network for an aperiodic subarray beamforming antenna is presented. The feed structure is divided into vertical and horizontal parts. Vertical parts have inclined slots with a reduced-height waveguide, and the horizontal part has unequal H-plane septum power dividers to achieve a compact feed network with acceptable electrical characteristics. The angle of each inclined slot and the position of each septum were designed for amplitude weighting and in-phase characteristics. For a comparison, a simple resonant feed network without septum power dividers (i.e., with waveguides and inclined slots) was simulated to access the effectiveness of the proposed network. The proposed structure was fabricated using computer numerical control milling and diffusion bonding. The input reflection coefficient was less than -15 dB, and the transmission phase difference between 20 ports was less than 72 ° within a bandwidth of 2.4%. This feed network design has potential applications in electronically scanned arrays and subarray antennas for a limited field of view.

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)

The design of aperiodic tiled array antennas for limited field-of-view (LFoV) applications is addressed. Starting from a finite alphabet of tile shapes, the configuration of the sub-arrays and their complex (amplitude and phase) weights are optimized to minimize the peak sidelobe level of a pencil beam within the LFoV scan region, while fulfilling geometrical constraints on the positions of the tiles to match a pre-defined topology of the feeding network (FN). In case of computationally-tractable array sizes, the global optimum of the synthesis problem at hand is yielded with an enumerative approach. Otherwise, sub-optimal trade-off tilings of the array aperture are synthesized by means of a customized optimization method based on a smart sampling technique. A set of representative benchmark problems, concerned with LFoV array applications, is described and discussed to assess the effectiveness of the proposed approach.

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)

In this paper, a sidelobe recognition method using boresight error and quadrant signal difference for a monopulse array is proposed. A conventional sidelobe recognition method compares the difference between the sum and delta channels. This method works well for the azimuth and elevation planes. However, the method is prone to many errors in the diagonal region of the two-dimensional plane. To overcome this problem, a method to calculate the deviation of the boresight error difference with different frequency combinations and a threshold to identify the sidelobe is proposed, and the method is validated to significantly reduce the error region. If a four-quadrant signal can be extracted separately, the signal deviation can be calculated and compared with the threshold, and the error region can be further reduced. The effects of each margin and bandwidth on the recognition performance are analyzed, and a slot array antenna is simulated to assess the method's effectiveness.